A version of AbstractQueuedSynchronizer in
which synchronization state is maintained as a long.
This class has exactly the same structure, properties, and methods
as AbstractQueuedSynchronizer with the exception
that all state-related parameters and results are defined
as long rather than int. This class
may be useful when creating synchronizers such as
multilevel locks and barriers that require
64 bits of state.

AbstractQueuedLongSynchronizer

Creates a new AbstractQueuedLongSynchronizer instance
with initial synchronization state of zero.

Method Detail

getState

protected final long getState()

Returns the current value of synchronization state.
This operation has memory semantics of a volatile read.

Returns:

current state value

setState

protected final void setState(long newState)

Sets the value of synchronization state.
This operation has memory semantics of a volatile write.

Parameters:

newState - the new state value

compareAndSetState

protected final boolean compareAndSetState(long expect,
long update)

Atomically sets synchronization state to the given updated
value if the current state value equals the expected value.
This operation has memory semantics of a volatile read
and write.

Parameters:

expect - the expected value

update - the new value

Returns:

true if successful. False return indicates that the actual
value was not equal to the expected value.

tryAcquire

protected boolean tryAcquire(long arg)

Attempts to acquire in exclusive mode. This method should query
if the state of the object permits it to be acquired in the
exclusive mode, and if so to acquire it.

This method is always invoked by the thread performing
acquire. If this method reports failure, the acquire method
may queue the thread, if it is not already queued, until it is
signalled by a release from some other thread. This can be used
to implement method Lock.tryLock().

arg - the acquire argument. This value is always the one
passed to an acquire method, or is the value saved on entry
to a condition wait. The value is otherwise uninterpreted
and can represent anything you like.

Returns:

true if successful. Upon success, this object has
been acquired.

Throws:

IllegalMonitorStateException - if acquiring would place this
synchronizer in an illegal state. This exception must be
thrown in a consistent fashion for synchronization to work
correctly.

arg - the release argument. This value is always the one
passed to a release method, or the current state value upon
entry to a condition wait. The value is otherwise
uninterpreted and can represent anything you like.

Returns:

true if this object is now in a fully released
state, so that any waiting threads may attempt to acquire;
and false otherwise.

Throws:

IllegalMonitorStateException - if releasing would place this
synchronizer in an illegal state. This exception must be
thrown in a consistent fashion for synchronization to work
correctly.

tryAcquireShared

protected long tryAcquireShared(long arg)

Attempts to acquire in shared mode. This method should query if
the state of the object permits it to be acquired in the shared
mode, and if so to acquire it.

This method is always invoked by the thread performing
acquire. If this method reports failure, the acquire method
may queue the thread, if it is not already queued, until it is
signalled by a release from some other thread.

arg - the acquire argument. This value is always the one
passed to an acquire method, or is the value saved on entry
to a condition wait. The value is otherwise uninterpreted
and can represent anything you like.

Returns:

a negative value on failure; zero if acquisition in shared
mode succeeded but no subsequent shared-mode acquire can
succeed; and a positive value if acquisition in shared
mode succeeded and subsequent shared-mode acquires might
also succeed, in which case a subsequent waiting thread
must check availability. (Support for three different
return values enables this method to be used in contexts
where acquires only sometimes act exclusively.) Upon
success, this object has been acquired.

Throws:

IllegalMonitorStateException - if acquiring would place this
synchronizer in an illegal state. This exception must be
thrown in a consistent fashion for synchronization to work
correctly.

arg - the release argument. This value is always the one
passed to a release method, or the current state value upon
entry to a condition wait. The value is otherwise
uninterpreted and can represent anything you like.

Returns:

true if this release of shared mode may permit a
waiting acquire (shared or exclusive) to succeed; and
false otherwise

Throws:

IllegalMonitorStateException - if releasing would place this
synchronizer in an illegal state. This exception must be
thrown in a consistent fashion for synchronization to work
correctly.

acquire

public final void acquire(long arg)

Acquires in exclusive mode, ignoring interrupts. Implemented
by invoking at least once tryAcquire(long),
returning on success. Otherwise the thread is queued, possibly
repeatedly blocking and unblocking, invoking tryAcquire(long) until success. This method can be used
to implement method Lock.lock().

Parameters:

arg - the acquire argument. This value is conveyed to
tryAcquire(long) but is otherwise uninterpreted and
can represent anything you like.

acquireInterruptibly

Acquires in exclusive mode, aborting if interrupted.
Implemented by first checking interrupt status, then invoking
at least once tryAcquire(long), returning on
success. Otherwise the thread is queued, possibly repeatedly
blocking and unblocking, invoking tryAcquire(long)
until success or the thread is interrupted. This method can be
used to implement method Lock.lockInterruptibly().

Parameters:

arg - the acquire argument. This value is conveyed to
tryAcquire(long) but is otherwise uninterpreted and
can represent anything you like.

tryAcquireNanos

Attempts to acquire in exclusive mode, aborting if interrupted,
and failing if the given timeout elapses. Implemented by first
checking interrupt status, then invoking at least once tryAcquire(long), returning on success. Otherwise, the thread is
queued, possibly repeatedly blocking and unblocking, invoking
tryAcquire(long) until success or the thread is interrupted
or the timeout elapses. This method can be used to implement
method Lock.tryLock(long, TimeUnit).

Parameters:

arg - the acquire argument. This value is conveyed to
tryAcquire(long) but is otherwise uninterpreted and
can represent anything you like.

acquireShared

public final void acquireShared(long arg)

Acquires in shared mode, ignoring interrupts. Implemented by
first invoking at least once tryAcquireShared(long),
returning on success. Otherwise the thread is queued, possibly
repeatedly blocking and unblocking, invoking tryAcquireShared(long) until success.

Parameters:

arg - the acquire argument. This value is conveyed to
tryAcquireShared(long) but is otherwise uninterpreted
and can represent anything you like.

acquireSharedInterruptibly

Acquires in shared mode, aborting if interrupted. Implemented
by first checking interrupt status, then invoking at least once
tryAcquireShared(long), returning on success. Otherwise the
thread is queued, possibly repeatedly blocking and unblocking,
invoking tryAcquireShared(long) until success or the thread
is interrupted.

Parameters:

arg - the acquire argument.
This value is conveyed to tryAcquireShared(long) but is
otherwise uninterpreted and can represent anything
you like.

tryAcquireSharedNanos

Attempts to acquire in shared mode, aborting if interrupted, and
failing if the given timeout elapses. Implemented by first
checking interrupt status, then invoking at least once tryAcquireShared(long), returning on success. Otherwise, the
thread is queued, possibly repeatedly blocking and unblocking,
invoking tryAcquireShared(long) until success or the thread
is interrupted or the timeout elapses.

Parameters:

arg - the acquire argument. This value is conveyed to
tryAcquireShared(long) but is otherwise uninterpreted
and can represent anything you like.

hasQueuedThreads

public final boolean hasQueuedThreads()

Queries whether any threads are waiting to acquire. Note that
because cancellations due to interrupts and timeouts may occur
at any time, a true return does not guarantee that any
other thread will ever acquire.

In this implementation, this operation returns in
constant time.

Returns:

true if there may be other threads waiting to acquire

hasContended

public final boolean hasContended()

Queries whether any threads have ever contended to acquire this
synchronizer; that is if an acquire method has ever blocked.

getQueueLength

public final int getQueueLength()

Returns an estimate of the number of threads waiting to
acquire. The value is only an estimate because the number of
threads may change dynamically while this method traverses
internal data structures. This method is designed for use in
monitoring system state, not for synchronization
control.

Returns:

the estimated number of threads waiting to acquire

getQueuedThreads

Returns a collection containing threads that may be waiting to
acquire. Because the actual set of threads may change
dynamically while constructing this result, the returned
collection is only a best-effort estimate. The elements of the
returned collection are in no particular order. This method is
designed to facilitate construction of subclasses that provide
more extensive monitoring facilities.

Returns:

the collection of threads

getExclusiveQueuedThreads

Returns a collection containing threads that may be waiting to
acquire in exclusive mode. This has the same properties
as getQueuedThreads() except that it only returns
those threads waiting due to an exclusive acquire.

Returns:

the collection of threads

getSharedQueuedThreads

Returns a collection containing threads that may be waiting to
acquire in shared mode. This has the same properties
as getQueuedThreads() except that it only returns
those threads waiting due to a shared acquire.

Returns:

the collection of threads

toString

Returns a string identifying this synchronizer, as well as its state.
The state, in brackets, includes the String "State ="
followed by the current value of getState(), and either
"nonempty" or "empty" depending on whether the
queue is empty.

hasWaiters

Queries whether any threads are waiting on the given condition
associated with this synchronizer. Note that because timeouts
and interrupts may occur at any time, a true return
does not guarantee that a future signal will awaken
any threads. This method is designed primarily for use in
monitoring of the system state.

getWaitQueueLength

Returns an estimate of the number of threads waiting on the
given condition associated with this synchronizer. Note that
because timeouts and interrupts may occur at any time, the
estimate serves only as an upper bound on the actual number of
waiters. This method is designed for use in monitoring of the
system state, not for synchronization control.

getWaitingThreads

Returns a collection containing those threads that may be
waiting on the given condition associated with this
synchronizer. Because the actual set of threads may change
dynamically while constructing this result, the returned
collection is only a best-effort estimate. The elements of the
returned collection are in no particular order.

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